The objectives of this project are to carry out studies to elucidate the biological properties of the mycoplasmas and to use these cells to investigate certain aspects of cellular and molecular biology for which they are good experimental systems. The specific goal for this proposal are in four areas: (1) cell cycle of M. gallisepticum, (2) mycoplasma chromosome structure, (3) physical mapping of the mycoplasma chromosome, and (4) mycoplasma phylogeny. The cell cycle studies will concentrate on the characterization of mycoplasma actin and its role in the cell cycle. Chromosome structure studies will examine mycoplasma nucleoids. Physical mapping will involve the construction of the map of a complete cell genome. The phylogeny studies will examine the conservation of 16S rRNA and actin sequences.